The present invention relates to a data reproducing apparatus, information processing apparatus, information processing method, and computer program. More particularly the invention relates to a data reproducing apparatus, information processing apparatus, information processing method, and computer program that are used in a contents management configuration, in which use limitations are defined, to perform a check-out for moving contents between information processing apparatuses and exercise efficient check-out/check-in management in a situation where contents are erased at a check-out destination.
As regards music data, image data, game programs, and other similar contents that are reproduced or used in a personal computer, reproducing apparatus, or other information processing apparatus, their creators and sellers generally own the copyright or distribution right for such data. Therefore, such contents are ordinarily used under the control of a contents management program that predefines a use limit to prevent the contents from being reproduced, duplicated, or manipulated without permission.
In recent years, particularly, recording apparatuses and recording media for recording information in digital form have been used widely. A digital recording technology makes it possible to record, duplicate, and reproduce video and audio data without degrading its quality. If, under these circumstances, recording media on which illegally copied contents are stored are distributed in the market, the profits of persons holding the copyrights of music, movie, and various other contents or persons having the rights to sell them will be diminished. Recently, various processing configurations have been worked out or proposed for use with digital recording apparatuses and recording media to prevent digital data from being illegally copied.
For example, the SDMI (Secure Digital Music Initiative), which proposes various music distribution technology specifications, has proposed a copyright protection standard for portable reproducing apparatuses. Various copyright protection schemes are proposed, including a limitation on the number of copies of contents, a limitation on the period of contents use, and check-out/check-in management, which will be described later.
Contents downloaded via a network by a user who performs a proper procedure and contents stored on a DVD or other recording medium can be reproduced on a personal computer or other information processing apparatus that is capable of reproducing contents. If an SDMI-defined limitation is imposed on the use of such contents, the personal computer or other information processing apparatus performs a contents use control process in accordance with an LCM (Licensed Compliant Module) or other software module compliant with the SDMI standard.
The LCM is a set of modules that exercise control to permit the use of individual contents only when the use conditions imposed by a copyright holder or other similar person are met. This LCM control is exercised to prevent copyrights from being infringed mainly by illegal secondary use of contents. Contents use conditions subject to control include contents reproduction conditions, copy conditions, move conditions, or storage conditions.
As an LCM-based contents use control process, check-out/check-in management is exercised to perform a process for managing the contents output to an external device and the contents input from the external device.
In a configuration for outputting contents targeted for management from a personal computer (PC) or other information processing apparatus, which performs a contents use management process, to portable devices (PDs) or other data reproducing apparatuses, which input the contents targeted for management as check-out contents, and allowing the portable devices to reproduce or use the contents, check-out/check-in management is exercised to provide contents use management by limiting the number of portable devices to which a set of contents can be output.
The outline of a check-out/check-in process and the configuration for enhancing the efficiency of a process for designating the contents to be checked out are disclosed, for instance, by Patent Document 1 (Japanese Patent Laid-Open No. 2001-175624). The configuration for acquiring check-out contents information from a portable device and making it possible to check out optimally selected contents is disclosed by Patent Document 2 (Japanese Patent Laid-Open No. 2003-77214).
When a check-out process is to be performed, the LCM of a personal computer that stores contents, for instance, on its hard disk performs authentication to check whether a portable device connected to the personal computer is authenticated. When the connected portable device is authenticated, the LCM performs an encryption or other similar process, transfers the contents, and if necessary, performs a process for transferring contents use rights information.
After performing a contents check-out process on the portable device, the LCM of the personal computer updates the contents use rights information (use conditions) about the checked-out contents. More specifically, the LCM decrements the permissible check-out count for the check-out contents by one. If, for instance, the maximum value for the permissible check-out count managed by the LCM of the personal computer is 3, the counter for keeping the permissible check-out count is decremented by one each time a check-out process is performed. As a result, the permissible check-out count is sequentially changed from 3 to 2, 1, and 0. When a permissible check-out count of 0 is reached, the associated contents cannot be checked out any more.
The portable device stores the check-out contents, which are input from the personal computer, and contents use rights information or the like on a flash memory or other recording medium. Thus, the portable device can reproduce or use the contents in accordance with the contents use rights information.
The contents checked out to the portable device can be returned to the personal computer's hard disk. The process for returning contents from the portable device to the personal computer is called a check-in process.
When a check-in is performed, the personal computer increments the permissible check-out count (counter) that is managed by the LCM. In other words, when contents are returned (checked in) from the portable device that has checked out the contents, the personal computer increments the counter by one. More specifically, the personal computer's contents counter is incremented by one upon each check-in so that the resulting count sequentially changes from 0 to 1, 2, and 3. As a result, the contents can be checked out repeatedly in accordance with an increase in the count.
At the time of a check-in process, the personal computer checks whether it performed a contents check-out for a portable device that requested a check-in process. The personal computer performs a check-in process only when a contents check-in process request is issued by a portable device for which the personal computer performed a check-out. If a portable device stores contents that are checked out from another personal computer, the check-in process will not be performed for such contents. For contents identification purposes, the personal computer acquires the device ID of a portable device for which a check-out is to be performed, associates the acquired device ID with check-out contents, and stores it in the personal computer's memory.
When the device ID is associated with contents and stored in the personal computer, a “virtual check-in process” can be performed as described below. If, for instance, contents checked out to a portable device from the personal computer are erased while the portable device is away from home, the personal computer detects when the portable device is connected to the personal computer that the checked-out contents are erased from the portable device. Further, when it is verified that a check-in process is not performed by the portable device, it is concluded that a check-in process is virtually performed. The counter for erased contents is then incremented by one. Due to this virtual check-in, the counter can be reset (incremented) even if checked-out contents are erased outside.
When the above virtual check-in process is to be performed, the personal computer performs a process for determining whether contents it checked out are erased from the portable device. In this instance, a targeted contents identifier is searched for. If the portable device has a small capacity and the amount of stored contents is small, the time required for the search does not constitute any problem. However, if the portable device has a hard disk or large-capacity flash memory, it stores a large amount of contents. In such a situation, it takes a considerable amount of time to search a large amount of contents for target contents.
To update the contents rights information of the personal computer's LCM (that is, to increment the permissible check-out count by one) in a situation where contents are erased by the portable device, it is necessary to perform a process for determining the contents ID that serves as the contents identifier corresponding to the erased contents.
The contents ID corresponding to the contents checked out by the portable device is recorded in a TOC (Table of Contents) file, which defines, for instance, the order of contents reproduction. Alternatively, the contents ID is recorded in a contents file, which stores contents.
If the portable device uses a TOC file for contents ID management purposes, the personal computer's LCM performs a process for verifying a contents ID that is registered in the portable device's TOC file. If a contents ID corresponding to checked-out contents is erased from the portable device's TOC file, the process verifies that the contents are erased.
However, if an enormous amount of data is stored in file form in the portable device, an enormous number of IDs are registered in the TOC file. It is therefore necessary to perform a process on an enormous amount of data to check for an ID corresponding to erased contents. It means that it is necessary to repeatedly perform a process on all contents IDs to check whether a contents ID corresponding to locally checked-out contents is registered in the portable device's TOC file. This causes a problem because the processing efficiency decreases with an increase in the number of check-out contents.
Further, contents IDs managed by the TOC file are not always erased when the portable device performs a contents erasure process. There is a problem with the fact that contents erasure can be verified only by conducting an ID search in the TOC file.
In a situation where the portable device uses contents storage files for contents ID management purposes, the personal computer's LCM must check all file names on the portable device to determine whether a file name corresponding to an erased contents ID exists. The efficiency of such a file search process is lowered if an enormous amount of data is stored in file form in the portable device.
As described above, if any contents are erased in a portable device after being checked out from a personal computer to the portable device in a situation where the portable device has a large-capacity recording medium and a large amount of check-out contents, a large amount of data needs to be searched within an erased contents verification process performed by the personal computer. As a result, the processing efficiency is decreased.